Electrostatic precipitator

ABSTRACT

A cabinet structure is formed with a central air flow chamber and a compartment at each end of the chamber. A web of dielectric filter medium extends across the air flow chamber between a pair of spaced apart, conductive grids insulated from the cabinet. The grids extend the full width of the compartment and a positive DC potential from a power pack is applied to the upstream grid, and a like negative potential is applied from a second power pack to the other grid. An ionizing assembly is arranged upstream from the grid structure and includes ionizing wires insulated from the cabinet and connected to the positive grid. Means is operable upon a predetermined reduction in air flow through the filter medium to effect advancement of a length thereof equal to the width of the air flow chamber.

United States Patent [1 1 Carr et al.

[4 1 Apr. 2, 1974 ELECTROSTATIC PRECIPITATOR [75] Inventors: Allan W. Carr,.Kirkvi1le; Donald C.

Wellman, Marcellus, both of N.Y.

[52] U.S. Cl 55/131, 55/138, 55/139,

55/149, 55/151, 55/155, 55/352, 55/354 [51] Int. Cl. B03c 3/12 [58] Field of Search 55/124, 126, 131, 132,

[56] References Cited UNITED STATES PATENTS 2,218,453 10/1940 Mickle 55/352 X 2,297,601 9/1942 Williams 55/132 2,502,560 4/1950 Dahlman 55/132 2,822,058 2/1958 Roos et al.... 55/131 2,873,000 2/1959 Elam 55/143 X 2,990,912 7/1961 Colc 55/130 2,996,810 8/1961 Cobb ct a1... 34/82 3,117,849 1/1964 Selke 55/142 X 3,350,853 11/1967 Revell... 55/354 3,350,854 11/1967 Revell 55/354 3,552,098 1/1971 Cochran 55/274 200 1 130 In no 3,626,668 12/1971 Cardiff 55/126 FOREIGN PATENTS OR APPLICATIONS 794,038 4/1958 Great Britain 55/154 44/27119 11/1969 Japan 55/124 Primary Examiner-Dennis E. Talbert, Jr. Attorney, Agent, or Firm-D. Emmett Thompson; Donald F. Daley [57] ABSTRACT A cabinet structure is formed with a central air flow chamber and a compartment at each end of the chamber. A web of dielectric filter medium extends across the air flow chamber between a pair of spaced apart, conductive grids insulated from the cabinet. The grids extend the full width of the compartment and a positive DC potential from a power pack is applied to the upstream grid, and a like negative potential is applied from a second power pack to the other grid. An ionizing assembly is arranged upstream from the grid structure and includes ionizing wires insulated from the cabinet and connected to the positive grid. Means is operable upon a predetermined reduction in air flow through the filter medium to effect advancement of a length thereof equal to the width of the air flow chamher.

3 Claims, 11 Drawing Figures PATENTED APR 2 I974 SHEH 1 F 7 PATENTEDAPR 2 I974 SHEET 3 OF 7 PATENTEDAPR 2:914 3300.509

SHEEI '4 IF 7 FIGS PATENTEDAPR 21914 3.800.509

SHEET 5 OF 7 PATENTEDAPR 24914 3800 509 sumserv ELECTROSTATIC PRECIPITATOR BACKGROUND OF THE INVENTION Air filtering apparatus has been devised wherein a socalled roll type filtering medium extends across the air passage from a supply roll of clean medium to a take-up roll. In one form of such apparatus, a signal lamp is energized if the air flow through the filter medium drops to a predetermined volume because the medium has become loaded with dirt particles. The take-up roll is then rotated manually to advance clean medium across the air flow. That arrangement requires the presence of an attendant.

In another form of apparatus, the take-up roll is rotated by a motor which is energized periodically by a timer. That form of apparatus is inefficient in that there are times when the filter medium becomes clogged up prior to operation of the timer. There are other instances when the timer effects advancement of the medium when it has not been clogged up sufficiently to require advancement of the medium.

This invention has as an object an electrostatic filter apparatus wherein a strong electrostatic field is maintained in a porous dielectric medium effecting the entrapment of particles, in the air flow, which have been previously charged by an upstream ionizing assembly. The invention also includes means operable, if the air flow through the medium drops to a predetermined value, to effect advancement of the medium continuously until a length of medium equal to the entire width of the air flow chamber has been advanced thereacross.

SUMMARY OF THE INVENTION A pair of conductive grid elements extend transversely of the air flow chamber in a cabinet and are insulated therefrom. A porous medium of dielectric is positioned between the grids. An ionizer assembly is mounted in the cabinet upstream from the grid structure. The upstream grid and the ionizing wires in the ionizing assembly are connected to the positive output potential of a DC power source. The grid on the downstream side of the medium is connected to the negative output potential ofa second power pack. Means is provided for advancing a length of filter medium across the air flow chamber coextensive with the width of the chamber when the air flow through the medium drops to a predetermined level.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevational view with parts broken away of an electrostatic precipitator embodying our invention;

FIG. 2 is a view taken on line 22, FIG. 1, with parts broken away;

FIG. 3 is a view taken on line. 33, FIG. 1;

FIG. 4 is a view taken on line 44, FIG. 2;

FIG. 5 is an isometric view of one of the ionizer sections removed from the cabinet and including a contiguous portion of the adjacent section;

FIG. 6 is a sectional view taken on line 66, FIG. 5;

FIG. 7 is a view similar to FIG. 6 but taken on line 7-7, FIG. 5;

FIG. 8 is an isometric view of the right end portion of the cabinet structure shown in FIGS. 1 and 2 with parts broken away, the view illustrating the relative orientation of the ionizer assembly and the electrostatic assembly;

FIG. 9 is an isometric view of the compartment shown at the right end of the cabinet structure in FIGS. 1 and 2 with the closure removed therefrom;

FIG. 10 is a fragmentary isometricview illustrating the medium measuring mechanism; and

FIG. 1 l is a schematic wiring diagram of the circuitry for the operation and control of the precipitator.

DESCRIPTION OF THE PREFERRED EMBODIMENT The precipitator consists of a cabinet structure having a main central portion serving as an air flow chamber and including a base 20, end walls 21, 22 and a top cover 24. Compartments 25, 27 are arranged at the ends of the cabinet center section. Each of these compartments is provided with a removable door 28.

The compartments 25, 27 are formed with rear walls 30, 31, side walls 32, 33, and bottom walls 35, 36. The compartments 25, 27 are completed by top walls 40, one of which is shown in FIG. 9. The forward edges 43 of the top walls 40 are spaced inwardly a distance from the plane of the front of the cabinet, and are formed with notches 45 to rotatably receive the upper ends of shafts 47, 48, the lower ends of which are journaled in the bottom walls 35, 36. A supply roll of filter medium is positioned on the shaft 47 in compartment 25. The used medium is collected on shaft 48 in compartment 27.

The precipitator includes an ionizing assembly arranged in the forward area of the cabinet structure and extending transversely thereof between the end compartments 25, 27. An upwardly facing channel member 50 is fixed at its ends to the end walls 21, 22 of the cabinet structure. A gusset bracket 53 is fixed to a member 55 of rectangular form in cross section, see FIG. 3. The member 55 is positioned on the bottom wall 20 and extends between the end walls 21, 22. The bracket 53 is fixed to the box member 55 at approximately the center of the cabinet structure. The bracket 53 serves to support the channel 50 at the middle thereof.

There is a downwardly facing channel member 59 fixed between the end walls 21, 22 in the upper portion of the cabinet structure, and is supported at its center by a gusset brace 60, similar to the brace 53, and attached to an upper transversely extending box member 61. The ionizer assembly is formed in three sections indicated at 63, 64, 65 in FIG. 1. The channel members 50, 59 serve as guide rails in which the ionizer sections are slidably mounted. In FIG. 5 of the drawings, the ionizer section 65 is shown removed from the cabinet structure and still attached to the adjacent end of the section 64.

Each ionizer section includes upper and lower support members 67, 68. The member 67 being in the form of an upwardly facing channel slidably mounted in the channel 59, and the member 68 is a downwardly facing channel slidably mounted in the channel 50. The channels 67, 68 are formed with slots extending inwardly from their forward edges for the reception of grounded electrodes 70. The electrodes 70 are in the form of tubular members, rectangular in cross section, see FIGS. 5, 6 and 7. The electrodes 70 are fixed to the support members 67, 68 as by welding.

A conductor bar 73 is mounted on insulators 74 fixed to the support 68. There is a similar conductor bar 77 mounted on insulators 78 attached to the upper support 67. Resilient rods 80 are affixed at their inner ends to the conductor bar 73, and similar rods 81 are affixed to the conductor bar 77. Ionizing wires 85 are connected at their ends to the resilient rods 80, 81 which serve to maintain the wires 85 under tension. The arrangement is such that the wires 85 are spaced medial of the electrodes 70. The conductor bar 73 of each ionizing section is connected to the bar 73 of the adjoining section by a jumper 87, see FIG. 5.

A spacer member is positioned between the ionizer section 63 and the end wall 21. A spacer 91 is positioned at the right end of the ionizer section 65. The spacers 90, 91 are of U formation with the ends of the sides bent to form flanges 93 which are fixedly secured to plates 95 which are attached to the end walls 21, 22 and form closures for openings in the end walls, see FIGS. 8 and 9. The openings are dimensioned so that when the plates 95 are removed from the end walls, together with the spacers 90, 91, the ionizer sections 63, 64, 65 may be moved outwardly, due to the sliding supporting engagement with the channel tracks 50, 59.

The ionizer sections are so removable by first removing the doors or closures 28 from the compartments 25, 27 as illustrated in FIG. 9.

A strip of compressible insulation material 97 is positioned between the right-hand electrode 70 of the section 65 and the spacer 91. Also, between the adjacent electrodes 70 of the sections 63, 64 and 64, 65, at the abutting ends of the sections. The strips 97 serve to permit the ionizer sections to be yieldingly forced together in the assembly when the plates 95 are affixed to the end walls 21, 22.

Referring to FIG. 6, a U-shaped metal clip 100 is attached to the channel support 68 of the section 64 and extends below the end of the electrode 70 of that section. The end of the clip 100 is bent upwardly and positioned in the lower end of the electrode 70 at the left end of section 65. A similar clip 101 is attached to the support channel 67 of the section 65, the clip extending over the upper end of the electrode 70 in that section, and the insulating strip 97, with the end of the clip extending downwardly into the electrode 70 of the adjoining section 64, see FIG. 7. The sections 63, 64 are clipped together in like manner.

When the closure plate 95 is removed from the end wall 22, and the ionizer sections are moved to the right, with the section 65 positioned exteriorly of the wall 22, upward movement of this section will detach the section 65 from the adjacent section 64. This detachment being accomplished by the structural arrangement of the clips 100, 101 which will be apparent. In like manner, when the section 64 is moved outside the cabinet, it may be detached from the section 63. This arrangement permits for the convenient removal of the ionizer sections for the purpose of cleaning the electrodes 70, and as will be apparent, the ionizer sections may be readily reinserted into the cabinet structure.

The filter assembly consists of a grillwork spaced forwardly from a similar grillwork 111, see FIGS. 2, 3 and 8. The lower end of the grill 110 has attached thereto an angle iron 112 positioned on insulators 113. The grill 111 is similarly supported on insulators 114, see FIG. 3. The insulators 113, 1 14 are fixedly mounted on a downwardly facing channel member 117, the sides of which are flanged outwardly and fixed to the bottom wall 20 of the cabinet. The upper ends of the grills 110,

111 are similarly connected to an upwardly facing channel member 118 fixed to the top wall 24. Insulators 120, 121 connect the upper ends of the grids to the support channel 1 18. A guide of channel formation 123 is fixed to the underside of the support member 118, and a similar channel member 125 is fixed to the support member 117.

The filter medium, in the form of a fibrous web, is positioned between the grids 110, 111. The medium is withdrawn from a supply roll 131 mounted on the shaft 47, the medium passing between curved guide members 132, 133 spaced apart to accept the compressed medium as it leaves the roll 131. The fibrous material of the medium is expansible when relieved from compression forces and fills the space between the grills 110, 111. Similar compression members 132, 133 are attached to the end wall 22, the medium extending through these compression members for rewinding on a roll 137 mounted on the shaft 48. The medium compression members 132, 133 provide sealing means at each end of the air flow chamber.

Means, as a blower, not shown, is provided for effecting an air flow through the air flow chamber of the cabinet structure as indicated by the arrows 140.

The ionizer assembly serves to charge the particles in the air flow in a well-known manner. The output of power pack 143, at positive potential, is applied to the ionizer wires 85 through line connected to the conductor bar 73. The line 145 is also connected to the grid 110 through branch line 146, see FIG. 11.

The output of the power pack 147, at negative potential, is connected to the grid 111 by line 150. The grids 110, 111 so charged, create an electrostatic field in the medium 130. The charged particles in the air flow passing from the ionizer assembly through the filter section are collected in the charged medium 130.

As the particles in the air flow are collected in the medium, the air flow through the medium is reduced, and there comes a time when the medium is clogged up to the extent that its efficiency drops below a desired level.

When this situation prevails, the medium 130 is advanced from the supply roll 131 between the grids 110, 111 and is wound up on the roll 137. Air flow sensing means is provided for sensing the volume of air flow through the filter means and uponsensing a predetermined reduction in the air flow, the take-up roll 137 is rotated continually until a length of medium equal to the spacing between the end walls 21, 22 has been advanced from the supply roll 131. A motor 153 is mounted in the compartment 27 and is operatively connected by a chain drive 155 to a stub shaft 156 journaled in the bottom wall structure 36. The lower end of the shaft 48 is detachably mounted in the stub shaft. When the motor 153 is energized, the wind up shaft 48 is rotated to wind the medium 130 thereon.

The air flow sensing means may be in the form of a differential pressure switch 157 operable on the pressure differential between the areas at the upstream and downstream sides of the filter means, although it will be appreciated that other air flow sensing arrangements may be employed to initially energize the motor 153.

Referring to FIG. 11, the power supply sides 160, 161 are energized by closing switch connections 163. One side of the pressure differential switch 157 is connected to the side 160 by wire 165. The other terminal of the switch is connected by line 166, 167 to line 168 connected to the motor-153. The opposite side of the motor is connected to line 161 by line 169.

Means is provided for measuring the advancement of the medium 130 to make certain that a new length of the medium is positioned between the grids 110, 111, the new length of medium extending from end wall 21 to end wall 22. Line 166 also extends to one terminal of a cam operated switch 170. This switch is actuated by a cam 171 affixed to the upper end of a shaft 173 journaled in a bearing structure, not shown, attached to switch box 175, see FIG. 10. The box 175 is attached to the underside of the top wall 40 of compartment 27. A drive wheel 177 is affixed to the lower end of the shaft 173, the periphery of which is provided with prongs or teeth, and a portion of the periphery extends through a slot 178 formed in the medium sealing guide strip 133. The arrangement is such that, upon advancement of the medium 130, rotation is imparted to the wheel 177 and, accordingly, to the cam 171. Accordingly, upon closing of the air flow sensing switch 157, the motor 153 is initially energized through the circuitry described above, and the lobe of the cam 171 moves out of engagement with the switch 170 to extend the circuit from line 166 through line 180, normally closed switch 181 to coil 182 of a step switch 183. Upon energization of the coil 182, the movable contact 184 of the step switch is moved to the first contact 185 of a connected series of contacts. The contact 186 at the end of the series is connected by line 190 to the line 168. The movable contact 184 is connected to the power supply side 160 by line 191.

It will be apparent that upon advancement of a predetermined amount of the medium 130, the cam 171 will make one revolution and the switch 170 will be opened and again closed, effecting de-energization and re-energization of the coil 182 to move the contact 184 to the next contact in the circular series. The switch 183 is provided with a sufficient number of fixed contacts, in relation to the diameter of the wheel 177, so that, upon the contact 184 moving through the series of fixed contacts, and moving from the last contact 186 in the series to the home position, as shown in FIG. 11, a length of medium has been advanced comparable to the width of the air flow chamber.

Line 168 may be connected to the supply side 160 through a manually operable switch 193 to energize motor 153. The switch 193 is connected to switch 181.

- When switch 193 is closed, switch 181 is opened.

An arm 195 is journaled at one end to the rear wall 30 of the compartment 25, see FIG. 2. The opposite end of the arm extends forwardly for engagement by the medium on the supply roll 131. When the supply of medium on roll 131 has become exhausted, the movement of the arm in proximity to the shaft 47 will operate a switch 200. The switch 200 and a manually operable switch 201 are connected in series in the side 160 of the supply, see FIG. 11. When the medium has become exhausted on roll 131, the switch 200 is moved into engagement with contact 203, thus interrupting the power supply to the motor control circuitry, and energizing a signal lamp 205. When a full roll of medium is positioned on the shaft 47, the arm 195 will return switch 200 to its normal position, as shown in FIG. 11. The purpose of the manually operated switch 201 is to permit the attendant to de-energize the motor operating circuitry during the removal of the wound up roll of used medium and installing a new roll of medium on shaft 47.

The power packs 143, 147 are connected to the side 160 through switches 204, 205 providing power to line 206, branch line 207 to power pack 143, the line 206 continuing to power pack 147. The opposite sides of the power packs are connected by lines 208, 209 to the opposite side 161. The separate power pack arrangement is advantageous in that it provides a high potential difference between the grids 110, 111 at substantially less cost than using a single power pack. For example, the output of power pack 143 through line may have a potential of 15,000 volts positive, the line having a negative potential of 15,000 volts, thereby providing 30,000 volts for establishing a high powered electrostatic field in the medium 130.

The switches 204, 205 are normally closed switches and are opened upon removal of the doors 28 from the compartments 25, 27. This arrangement assures that the high voltage circuitry will be de-energized during the removal of the used medium, and the installation of a new roll on shaft 47 and the threading of the new medium between the grids 110, 111.

A protective screen 215 is fixed in the front opening of the air flow compartment. Closing of the pressure switch 157 energizes a starting circuit for motor 153 through wires 166, 167, 190, 168. Immediately upon advancement of the medium, cam 171 will close switch 170, energizing the step switch coil 182 effecting movement of the contact 184 to the first fixed contact 185. This operation assures energization of a running circuit for the motor 153. As previously stated, contact 184 is connected to the side by wire 191.

It will be apparent upon advancement of the medium that the switch is periodically actuated by the cam 171. Accordingly, the running circuit for the motor 153 is maintained until the contact 184 returns to normal, or home position, as shown in FIG. 11. The cycle of the contact 184 is in accordance with the amount of medium advanced and the arrangement of the measuring wheel 177, and the steps provided in the step switch 183, are such as to advance a length of medium equal to the space between the end walls 21, 22.

As the clean medium is advanced from the supply, the volume flow of air through the medium may be such as to open the contacts of switch 157. However, that will not interfere with the operation of motor 153, because the running circuit is under the control of the step switch 183.

While a preferred embodiment of this invention has been described for purposes of illustration, it will be appreciated that this invention may be otherwise embodied within the scope of the following claims.

We claim:

1. An electrostatic precipitator of the type wherein particles entrained in air are electrostatically charged and collected in a filter medium comprising i a. a cabinet structure formed with an airflow chamher for the passage of an airflow therethrough,

a filter medium supply compartment at one end of said chamber, and

a filter medium collection compartment at the opposite end of said chamber;

b. filter means associated with said chamber including a pair of grid structures formed of electrically conductive material extending in parallel spaced apart relation across said chamber from one end thereof to the opposite end, each of said grids being insulated from said cabinet,

a first power supply means for applying a positive DC potential on one of said grids and a second power supply for applying a negative potential to the other of said grids,

a web of nonconductive filter medium extending across said chamber and disposed intermediate said grids, a supply roll of filter medium journaled in said supply compartment,

a medium take-up roll journaled in said collection compartment, and

a motor connected to the take-up roll and operable when energized to effect rotation of the take-up roll for the advancement of said medium from the supply roll across the chamber;

. an ionizing assembly arranged in said chamber upstream from said filter means including a linear series of spaced apart electrodes extending transversely of said airflow chamber, and

ionizer wires disposed intermediate said electrodes, said wires being insulated from said electrodes and said cabinet structure,

said positive potential from said first power supply being connected to said ionizer wires;

d. and control means including airflow sensing means for sensing the volume of airflow through said filter medium,

said airflow sensing means being electrically connected to said motor to energize the motor for advancement of the filter medium upon the sensing of a predetermined reduction in airflow through said filter medium,

a drive member engaging and rotated by the filter medium,

a stepping switch electrically connected to the motor to control the time of operation of the motor,

a pulsing switch electrically positioned to advance the stepping switch, and

a cam driven by the drive member and positioned to actuate the pulsing switch as the filter medium rotates the drive member.

2. An electrostatic precipitator according to claim 1 wherein the stepping switch has a number of steps sufficient to allow operation of the motor for a time sufficient to advance a length of filter medium equal to the width of the chamber.

3. An electrostatic precipitator according to claim 1 wherein said ionizing assembly includes upper and lower supporting rails mounted in said airflow chamber and extending transversely thereof,

a plurality of ionizer sections, each of said sections having upper and lower support members,

a series of spaced apart electrodes fixedly secured at their ends to said support members,

ionizer wire supporting means arranged intermediate each pair of said electrodes and being insulated therefrom, an ionizer wire disposed intermediate each pair of said electrodes and extending in parallel spaced relation thereto,

said ionizer wires being attached to said wire supporting means, and said support members being slidably mounted in said supporting rails. 

1. An electrostatic precipitator of the type wherein particles entrained in air are electrostatically charged and collected in a filter medium comprising a. a cabinet structure formed with an airflow chamber for the passage of an airflow therethrough, a filter medium supply compartment at one end of said chamber, and a filter medium collection compartment at the opposite end of said chamber; b. filter means associated with said chamber including a pair of grid structures formed of electrically conductive material extending in parallel spaced apart relation across said chamber from one end thereof to the opposite end, each of said grids being insulated from said cabinet, a first power supply means for applying a positive DC potential on one of said grids and a second power supply for applying a negative potential to the other of said grids, a web of nonconductive filter medium extending across said chamber and disposed intermediate said grids, a supply roll of filter medium journaled in said supply compartment, a medium take-up roll journaled in said collection compartment, and a motor connected to the take-up roll and operable when energized to effect rotation of the take-up roll for the advancement of said medium from the supply roll across the chamber; c. an ionizing assembly arranged in said chamber upstream from said filter means including a linear series of spaced apart electrodes extending transversely of said airflow chamber, and ionizer wires disposed intermediate said electrodes, said wires being insulated from said electrodes and said cabinet structure, said positive potential from said first power supply being connected to said ionizer wires; d. and control means including airflow sensing means for sensing the volume of airflow through said filter medium, said airflow sensing means being electrically connected to said motor to energize the motor for advancement of the filter medium upon the sensing of a predetermined reduction in airflow through said filter medium, a drive member engaging and rotated by the filter medium, a stepping switch electrically connected to the motor to control the time of operation of the motor, a pulsing switch electrically positioned to advance the stepping switch, and a cam driven by the drive member and positioned to actuate the pulsing switch as the filter medium rotates the drive member.
 2. An electrostatic precipitator according to claim 1 wherein the stepping switch has A number of steps sufficient to allow operation of the motor for a time sufficient to advance a length of filter medium equal to the width of the chamber.
 3. An electrostatic precipitator according to claim 1 wherein said ionizing assembly includes upper and lower supporting rails mounted in said airflow chamber and extending transversely thereof, a plurality of ionizer sections, each of said sections having upper and lower support members, a series of spaced apart electrodes fixedly secured at their ends to said support members, ionizer wire supporting means arranged intermediate each pair of said electrodes and being insulated therefrom, an ionizer wire disposed intermediate each pair of said electrodes and extending in parallel spaced relation thereto, said ionizer wires being attached to said wire supporting means, and said support members being slidably mounted in said supporting rails. 